Air conditioner with receiver in accumulator

ABSTRACT

IN THE PREFERRED FORM, THE REFRIGERANT CIRCUIT IS PROVIDED WITH A RECEIVER PRECEDING THE CAPILLARY TUBE RESTRICTOR WHICH IS LOCATED WITHIN THE ACCUMULATOR AT THE OUTLET OF THE EVAPORATOR FOR PRECOOLING THE LIQUID REFRIGERANT TO SUSTANTIALLY PREVENT ELECTROSTATIC PRECIPITATION IN THE CAPILLARY TUBE RESTRICTOR.

United States Patent [56] References Cited UNITED STATES PATENTS 6/1946Carter..........................

[72] Inventor James W. Jacobs -Dayton,0hio 211 AppLNo. 808,097

2,740,263 4/1956 Kritzer Primary Examiner-Martin P. Schwadron AssistantExaminer-P. D. Ferguson AttorneysWil1iam S. Pettigrew, Frederick M.Ritchie and [22] Filed Mar. 18,1969

[45] Patented June 28, 1971 [73] Assignee General Motors CorporationDetroit, Mich.

Edward P. Barthel 54 AIR CONDITIONER minimum in ACCUMULATOR ABSTRACT: Inthe preferred form, the refrigerant circuit is lClaim, 2 Drawing Figs.

' provided with a receiver preceding the capillary tube restrictor whichis located within the accu mulator at the outlet of the evaporator forprecooling the liquid refrigerant to substantially prevent electrostaticprecipitation in the capillary tube restrictor.

[51] [50] FieldofSearch...................

PATENTED JUN28 um ATTORNFY AIR CONDITIONER WITII RECEIVER INACCUMULA'IOR It has been recognized that the commonly used refrigerantsin air conditioning systems gradually form rough deposits within thecapillary tube restrictors so that the refrigerant flow is graduallyreduced during the life of the refrigerating system to gradually reduceits capability of producing cold. It has been recognized that this is aresult of the streaming potential produced by the rapid flow ofrefrigerant vapor through the capillary tube restrictor which produces astreaming potential of the order of 10,000 to 100,000 volts which tendsto make the capillary tube restrictor an electrostatic precipitator.

It is an object of this invention to precool the liquid refrigerantprior to its entrance into the capillary tube restrictor substantiallyto evaporator temperature so as to reduce the evaporation of therefrigerant and the formation of gas within the restrictor sufficientlyto reduce the velocity of flow and substantially reduce the streamingpotential and electrostatic precipitation within the restrictor.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred embodiment of the present invention isclearly shown.

IN THE DRAWINGS FIG. I is a view partly diagrammatic of an airconditioning refrigerating system embodying one form of my invention;and

FIG. 2 is a fragmentary side view of the accumulator and receiver andthe adjacent portions of the restrictor and evaporator shown in FIG. 1.

Referring now to the drawings, enclosed in an air conditioner cabinet 19indicated in dot-dash outline, there is shown a sealed motor compressorunit 20 containing an electric motor and a compressor. The sealed unit20 withdraws evaporated refrigerant through the suction conduit 22 anddischarges the compressed refrigerant through the discharge conduit 24which connects with the top of the vertically finned tubular condenser26. This condenser is located in one end of the cabinet and is cooled byair circulated by the propeller fan 28 connected to the fan motor 30.The compressed refrigerant is thereby liquefied and flows to the bottomof the condenser from which it is conducted by the supply pipe 32 to areceiver 34 from which the liquid refrigerant flows through thecapillary tube restrictor 36 to the bottom of the vertically finnedtubular evaporator 38. The air to be cooled is circulated through theevaporator 38 by a propeller type fan 40 which may draw air from thesides and bottom and top and discharge the air through the evaporator38. The circulating air causes the evaporation of the refrigerant whichflows upwardly through the evaporator to the accumulator 42 in theoutlet portion of the evaporator. The top of the accumulator connects tothe suction conduit 22.

It has been discovered that when air conditioning systems employingcapillary tube restrictors and certain refrigerants operate under hightemperature conditions for long periods of time that their coolingcapacity is gradually reduced due to the accumulation of rough depositsadjacent the outlet portion of the capillary restrictor tubes. Thisappears to be the result of the streaming potential of l0,000 to l00,000volts which may be generated by the high velocity of vapor flow in thecapillary tube restrictor under such high temperatures and toelectrochemical properties of refrigerants. Refrigerants having aconductivity between ohm"cm. and 2.0 l0"ohm cm. are prone to capillarydeposit production. The precipitation is more severe for refrigerantshaving a conductivity between l0" and l0"ohm"cm.. Specific examples ofrefrigerants commonly used in air conditioning systems having the mostsevere problems of electrostatic precipitation are those known as R22and R502. R22 is monochlorodifluoromethane (CHCIF and R502 is anazeotropic mixture of R22 and chloropentafluoroethane (CHClF lCclF CFAccording to my invention, I precool the liquid flowing to the entranceof the restrictor 36 substantially to evaporator temperature byobtaining high heat transfer between the cold refrigerant in theaccumulator 42 and the warm liquid refrigerant in the receiver 34. Thisis done by locating the receiver 34 in the form of a relatively largetank substantially entirely within the accumulator 42 so that thereceiver 34 and its contents are cooled by being surrounded by the coldrefrigerant in the accumulator 42 which serves to keep the liquidrefrigerant in the evaporator and facilitates the return of completelyevaporated refrigerant through the suction conduit 22. The receiver 34is located adjacent the bottom of the accumulator 42 so that it will becontacted and cooled substantially to evaporator temperature by anyliquid refrigerant collecting in the bottom of the accumulator 42 andevaporating at the surfaces of the receiver 34.

This accumulator arrangement will aid in preventing any liquidrefrigerant from entering the suction conduit 22 and returning to thesealed unit 20. The heat transfer may be further augmented by the use ofany of the various forms of roughened or extended surfaces upon thereceiver 34. The receiver 34 is shielded from the air circulated by thefan 40 by being enclosed in the accumulator 42 so that its content ofliquid refrigerant is cooled to and maintained at a relatively lowtemperature during both the operating and idle periods of the apparatussubstantially at the temperature of the evaporator 38. A relativelylarge amount of cooled liquid refrigerant normally accumulates in thereceiver 34 under low pressure conditions in the condenser for normalrelease to provide increased cooling under high condenser temperatureand pressure conditions.

As a result of this precooling of the refrigerant in the receiver 34 theamount of evaporation and the amount of vapor formed in the refrigerantis greatly reduced. Since the volume of the liquid refrigerant is verysmall (about one-sixtieth compared to the volume of evaporatedrefrigerant, the velocity of the refrigerant flow within the capillarytube restrictor is greatly reduced thereby greatly reducing thestreaming potential and the electrostatic precipitation and theaccumulation of deposits within the capillary tube restrictor.

In addition to placing the receiving 34 within the accumulator 42, asshown in FIG. I, the capillary restrictor 36 may be also bonded to theoutside of the accumulator 42 and also to one or more passes or loops ofthe tubing of the evaporator 38 to provide additional heat transfer andcooling for the refrigerant in the capillary tube restrictor to maintainthe refrigerant in a liquid state in the capillary tube restrictor tothe greatest extent possible. Thus, by this large precooling of theliquid refrigerant in the receiver and also by the cooling of thecapillary tube restrictor, evaporation is substantially diminished inthe restrictor so that the velocity of flow and streaming potential aregreatly diminished, thereby substantially reducing deposits in thecapillary tube.

While the embodiment of the invention as herein disclosed constitutes apreferred form, it is to be understood that other forms might beadopted.

Iclaim:

1. An air conditioner including a motor compressor unit, a condenser, acapillary tube restrictor constituting a major restriction to flow and afin and tube evaporator connected in an operative refrigerant circuitcontaining a refrigerant capable of generating high streaming potentialforming substantial objectionable deposits in the capillary tuberestrictor wherein the improvement comprises providing the outletportion of the evaporator with a large accumulator and a receiverextending within and being substantially surrounded by the accumulatorin intimate heat transfer contact therewith, said receiver beingconnected between the outlet of said condensing means and the inlet ofsaid restrictor for precooling the liquid refrigerant prior to itsentrance into the restrictor tube, said evaporator comprising arefrigerant tube extending in heat transfer with a plurality of fins,said restrictor tube having a portion extending along and in direct heattransfer contact with a portion of said refrigerant tube which isprovided with the fins to provide additional cooling of the refrigerantas it flows through the restrictor.

+29 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,587 245 Dated June 28, 1971 Inventor s) Iames H Ia b It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 64, "10 should read l0 "7 same line, "ohm should read ohmsame line, "cmshould read cm same line, 2;.0 x 10 should read same line,"ohm should read ohm line 67, "10 should read 1o" same line, "10 shouldread 10 --7 same line, "ohm should read ohm same line, "cm. should readcm same column 1, line 65 "cm. should read cm Signed and sealed this22nd day of February 1972.

(SEAL) Attest:

EDWARD M.FLE'ICHER,JR. ROBERT T HALK Attesting Officer Commissioner ofPatents

